from tkinter import *
import math

def Square(radius):

    return math.pi * radius**2

def calculate_square():
    radius = float(radius_entry.get())
    try:
      square = "%11.3f" % Square(radius)
    except:
        square = "?"
    square_label.configure(text=square)

root = Tk()
root.title("eee")
frame = Frame(root)
frame.pack()

radius_entry = Entry(frame, width=100)
radius_entry.grid(row=0, column=0)
entry = Entry(frame, width=10)
entry.grid(row=1, column=1)

square_label = Label(frame, text="?")
square_label.grid(row=0, column=1)
eval_button = Button(frame, text="Calculate", width=10,
                     command=calculate_square)

eval_button.grid(row=1, column=0)
exit_button = Button(frame, text="Exit", width=10,
                     command=root.destroy)
exit_button.grid(row=1, column=1)

root.mainloop()
